package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;


@Component
@Slf4j
public class CacheClient {
    @Resource
    private StringRedisTemplate stringRedisTemplate;

    public void set(String key, Object value, Long time, TimeUnit timeUnit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,timeUnit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit timeUnit) {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(timeUnit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback, Long time, TimeUnit timeUnit) {
        String key = keyPrefix + id;
        //从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //存在直接返回
            return JSONUtil.toBean(json, type);
        }
        //命中是否是空值
        if (json != null) {
            //返回错误信息
            return null;
        }
        //不存在根据id查询数据库
        R r = dbFallback.apply(id);
        //不存在，返回错误
        if (r == null) {
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //存在写入redis
        this.set(key, r, time, timeUnit);
        //返回
        return r;
    }
    //线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R, ID> R queryWithLogicalExpire(
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        // 1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        // 2. 缓存空缺：去数据库，并回填
        if (StrUtil.isBlank(json)) {
            // 2.1 DB 查询
            R newR = dbFallback.apply(id);
            if (newR == null) {
                // 2.2 空值缓存（短 TTL，防穿透）
                stringRedisTemplate.opsForValue().set(key, "", NULL_TTL, TimeUnit.SECONDS);
                return null; // 交由 Controller 返回“店铺不存在”
            }
            // 2.3 用“逻辑过期”结构回填并直接返回数据
            setWithLogicalExpire(key, newR, time, unit);
            return newR;
        }
        // 4.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        // 5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())) {
            // 5.1.未过期，直接返回店铺信息
            return r;
        }
        // 5.2.已过期，需要缓存重建
        // 6.缓存重建
        // 6.1.获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        // 6.2.判断是否获取锁成功
        if (isLock){
            // 6.3.成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    // 查询数据库
                    R newR = dbFallback.apply(id);
                    // 重建缓存
                    this.setWithLogicalExpire(key, newR, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    // 释放锁
                    unlock(lockKey);
                }
            });
        }
        // 6.4.返回过期的商铺信息
        return r;
    }

    public <R,ID> R queryWithLogicalExpire2(
            String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback, Long time, TimeUnit timeUnit) {
        String key=keyPrefix+ id;
        //从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        R r = null;
        //判断是否存在
        if (!StrUtil.isBlank(json)) {
            //存在，返回null
            //命中需要先把json反序列化为对象
            RedisData redisData = JSONUtil.toBean(json, RedisData.class);
            r = JSONUtil.toBean((JSONObject) redisData.getData(),type);
            LocalDateTime expireTime = redisData.getExpireTime();

            //判断是否过
            if (expireTime.isAfter(LocalDateTime.now())) {
                //未过期直接返回店铺信息
                return r;
            }
        }
        //已过期需要缓存重建
        //获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //判断是否过去锁成功
        if (isLock) {
            //成功，开启独立线程，实现缓存重建
//            CACHE_REBUILD_EXECUTOR.submit(() -> {
            try {
                //重建缓存
                R r1 = dbFallback.apply(id);
                this.setWithLogicalExpire(key, r1, time, timeUnit);
                return r1;
            } catch (Exception e) {
                throw new RuntimeException(e);
            } finally {
                //释放锁
                unlock(lockKey);
            }
//            });
        }
        //返回过期商户信息
        return r;
    }
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }
}
